Motor vehicles typically feature seat belts for protecting the occupants in case of an accident. In this respect, it is common practice to use automatic seat belts that are retracted when they are not in use. A so-called automatic seat belt retractor serves for realizing the retraction.
DE 10 2013 004 784 A1 discloses an automatic seat belt retractor. The seat belt retractor is provided with a retractor shaft and a device for determining the rotational speed and/or the rotational angle of the retractor shaft, a rotating magnetic element, a stationary magnetic field sensor and a magnetic flux-conducting stationary element between the rotating magnetic element and the magnetic field sensor. Information on the rotational angle of the retractor shaft is required for certain functions of seat belt retractors, particularly seat belt tensioners. This information is required, for example, for detecting the Out-Of-Position situation, for monitoring and controlling the rotational speed of the motor for driving the tensioner or a prelensioner or for controlling the tensioning process itself.